The present invention relates to a method and apparatus for inspecting or transferring material at preselected positions in a rectangular array of rows and columns. In particular, the present invention is directed to a method and apparatus for automatically inspecting or transferring material at one or more preselected positions in a rectangular array by scanning every row of the array in the same direction.
Various machines are known in the art for automatically sampling the contents of a plurality of containers arranged in a rectangular array. In general, the machines can be distinguished by the particular patterns which they trace in scanning the containers. The more complex the pattern traced by the machine during a scan of the container array, the more complex the mechanical structure of the machine.
The most common type of pattern used to scan a rectangular array of containers is the boustrophedon pattern. More particularly, a transfer tube, probe, or other element for inspecting or transferring material, hereinafter referred to generally as a "sampling element" for ease of reference, is transported across adjacent rows of containers in opposite directions. A machine which traces this type of pattern while scanning an array of containers is described in U.S. Pat. No. 3,205,921 entitled Liquid Fraction Collecting Apparatus issued to Packard et al. In this patent, the sampling element is transported in a stepped boustrophedon pattern wherein the sampling element is stopped at every column position in a row. Two stepping motors are required to drive associated pulleys and cables to transport the sampling element in predetermined increments along the columns and rows of the container array.
The deficiencies in scanning an array of containers by predetermined increments in a boustrophedon pattern are three-fold. First, there may be containers in the array which are empty or which contain materials which cannot be sampled until a later time. Obviously, it is desirable to pass over these containers and pause to sample only those containers containing material ready for sampling. If the sampling element is transported in predetermined increments and caused to stop at each column position in each row of the container array, a considerable portion of time can be wasted in examining empty containers or containers which hold material not ready for sampling. Second, to drive the sampling element from row to row in a boustrophedon pattern requires two separate motors, one for driving the sampling element from the first column position of a row to the last column position, and the other motor for driving the element from the last position in the latter row to the last position in the next adjacent row. The operation of the motors is complex since they must work in synchronization with a plurality of intricate indexing mechanisms. Third, a machine which operates in the boustrophedon pattern requires bidirectional controls, increasing the possibility of machine malfunction.
Scanning patterns other than the boustrophedon pattern are also well-known in the art. For example, in U.S. Pat. No. 3,168,124 entitled Fraction Collector issued to Lenkey, there is described a machine for sampling the contents of containers arranged in a rectangular array by transporting the sampling element in predetermined increments across each column in the array. When the sampling element reaches the last container in a column, it flies back to the first container in the same column and advances to the next column in the array. The sampling element must pause at each container in the column, whether or not the container is empty or contains material not ready to be sampled. In the extreme, entire columns of the container array may include no containers having contents ready for sampling. Nonetheless, the sampling element must stop at each container. Considerable amounts of time can be wasted by transporting the sampling element in predetermined increments regardless of the state of the contents of the containers.
It is also known in the art to automatically scan one or more preselected containers in a rectangular array. For example, U.S. Pat. No. 3,143,393 entitled Apparatus for Automatically Performing Chemical Operations and Similar or Related Operations issued to des Hons, describes a machine for automatically sampling containers at preselected orthogonal coordinates of an array. Two separate motors are required to drive the probe to scan the array of containers. Furthermore, to enable automatic operation of the machine, the machine must be electrically preset by means of relays, and the two motors must be mechanically connected to contact arms and camming wheels which operate in synchronism. The contact arms and camming wheels are connected, through gearing, to the motor shaft, forming an elaborate mechanism.
A primary advantage of the present invention is to automatically inspect or transfer material at one or more preselected positions in a rectangular array.
A further advantage of the present invention is to provide a simple mechanical means for preselecting those positions in the array at which material is to be inspected or transferred.
Another advantage of the present invention is to automatically scan a rectangular array of positions without allocating machine time to examining positions in the array at which material is not to be inspected or transferred.
A still further advantage of the present invention is to automatically scan predetermined rows of the array in one direction only, and to advance from row to row without scanning a row more than once.
Yet another advantage of the present invention is to provide a relatively simple and efficient control mechanism for transporting a sampling element along a row of the array without pausing at positions in the row which are not ready for sampling and without separate directional controls.